Oral inflammation is associated with common oral conditions, including periodontitis, for example. Gingivitis is the initial stage of gum disease. A cause of gingivitis is plaque, which is a soft, sticky, colorless film of bacteria that forms on the teeth and gums. Plaque, if left untreated, produces toxins that can inflame or infect the gum tissue to cause gingivitis. Untreated gingivitis can eventually spread from the gums to the ligaments and bone that support the teeth, and can cause periodontitis. Rutin (IUPAC name: 2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-3-[α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranosyloxy]-4H-chromen-4-one; CAS no: 153-18-4) is a glycoside formed by the flavonol quercetin and the disaccharide rutinose and has the structure below:

Rutin is found in a variety of plants, including rue (Ruta graveolens), mulberry leaf, Houttuynia cordata Thunb, Sophora japonica L., certain varieties of buckwheat, citrus, and apple. Rutin inhibits platelet aggregation and is believed to have anti-oxidant and anti-inflammatory properties. However, rutin is only poorly soluble in water (solubility ca. 13 mg/100 mL), and this property significantly restricts its delivery and effectiveness in oral care formulations. There is therefore a need in the art for oral care formulations which allow for the more effective delivery of rutin.
UK Patent No. 1,308,483 discloses preparations for the care of the teeth and the mouth. Example 2 of this document discloses a toothpaste comprising the sodium salt of the sulfuric acid ester of rutin in an amount of 0.20 wt % and glycerol (86%) in an amount of 10.00 wt %. It will be appreciated that the sulfuric acid ester of rutin discussed in the document has a different chemical structure to that of rutin itself.
U.S. Pat. No. 5,258,173 discloses a dentifrice composition comprising a stannous compound that releases stannous ions in the composition, such as stannous fluoride or stannous pyrophosphate. Rutin is identified as one of a series of antioxidants which may be included in the composition. No compositions comprising rutin are exemplified. The problem of improving the solubility of rutin in an oral care composition is not addressed by U.S. Pat. No. 5,258,173.